In the IEEE Transactions on Antennas and Propagation Vol. 51 No. 7 Jul. 2003 pages 1572-1581 an article has been published titled “Green's function for an Infinite Slot Printed Between Two Homogeneous Dielectrics, Part I: Magnetic Currents”, by Andrea Neto and Stefano Maci. A second part of this article has been published in the IEEE Transactions on Antennas and Propagation Vol. 52 No. 3 Mar. 2004, on pages 666-676. The first article mentions the possibility of building a sub-millimeter wave receiver that is integrated with a dielectric lens and that contains a slot printed on an infinite slab.
The articles describe the properties of electromagnetic waves that travel along a structure with a conductive ground plane that contains a narrow elongated non-conductive slot, when two dielectric media with different dielectric constants ε1 ε2 are present on opposite sides of the ground plane. It is shown that in this configuration a wave travels along the length of the slot, and that part of the wave energy is radiated under a predetermined angle relative to the ground plane.
The articles refer to the possibility of using this phenomenon to realize a leaky wave antenna, but give no details about the structure of such an antenna. In a leaky wave transmission antenna an electromagnetic wave travels along a wave guiding structure so that at successive points along the structure each time a fraction of the wave energy is radiated to the far field. As a result the wave energy gradually decreases along the structure. The travelling wave defines predetermined phase relationships between the radiation from different points along the structure and thereby a direction (if any) in which the radiation from the points leads to coherently radiation, so that the structure acts as an antenna. Usually, leaky wave antennas have a limited bandwidth, which is defined by the characteristic dimensions of the wave guiding structure.